Improvement in circuits and apparatus for duplex telegraphy



J. B. STEARNS.

Improvement in Circuits and Apparatus for Duplex Telegraphy.

Patented Nov. 12,1872.

5/ 73 I, inc

N S E D M P .5 M R 0 B S m X N 0 C m u m w I.- m M F M. 4

UNITED STATES PATENT OFFICE.

JOSEPH B. STEARNS, OF BOSTON, MASSACHUSETTS.

IMPROVEMENT lN CIRCUITS AND APPARATUS FOR DUPLEX TELEGRAPHY.

Specification forming part of Letters Patent No. 132,931, dated November 12, 1872.

OAsE B.

To all whom it may concern:

Be it known that I, J OSEPH B. STEARNS, of Boston, in the county of Suffolk, State of Massachusetts, have invented an Improvement in Telegraph Apparatus, of which the following.

is a specification:

This invention relates to apparatus for the simultaneous transmission of two signals from opposite ends of the same line-wire; and consists in the method of enabling either main station at the ends of the line to maintain correspondence with one or more way stations.

The accompanying drawing forming part of this specification, represents my invention, in which- A represents the receiving apparatus at the main station; B, the electro magnetic key used in corresponding with the other main station; D, a common lever-key for corresponding with the way station or stations; (3, the receiving instrument at a way station; and F a lever-key at the same.

The apparatus for double transmission, in which this improvement is used, is the form described in my Letters Patent No. 78,548, of June 2, 1868, which, for the purpose of more clearly explaining my present invention, I will briefly describe.

The receiving apparatus at each main station at the ends of the line consists of two electro-maguets, opposed to each other, and having a common armature, or arranged so as to act upon two armatures on the same lever.

The current from the main battery, before passing through the receiving instrument, divides into two branches-one part passing through a magnet connected with the line, the other part through an opposing magnet and a resistance-coil to the earth. When the circuit is closed by means of the electromagnetic key, as represented in the drawing, both magnets are equally excited, and the armatures, being equally attracted, the armaturelcver does not move, but remains against the back contact, so that though a current passes through the instrument to the line no signal is given by it; but when the current comes from the distant station it passes through one magnet only, on account of the resistance in the circuit through the other magnet, and consequently the armature is attracted and the lever strikes against its front contact. Thus, as each receiving instrument responds only to the currents from the distant station, simultaneous transmission between both stations is possible.

When the line has way stations with which it is desired to maintain correspondence, the

receiving instruments at these way stations are placed in the circuit, which also passes through a key, as shown at F. By breaking contact at F the circuit from the distant station, passing through the receiving instrument at each main station, is interrupted, and notice is given thereby that the way station wishes to communicate, which it does by means of the key F. When a main station sends to the way station, the electromagnetic key used in sending to the other main station cannot be used for the reason that it never interrupts the circuit from 'the other main station, but merely puts on an additional current from its own battery, the battery at the distant station remaining on during such time, and af fects the receiving instrument at the way station. It is therefore necessary to use at each main station a key, D, which is placed in the line between the place where the current passing to the main receiving instrument divides and the way instrument, which key breaks the circuit from the other stations batteries on the line, and thus efl'ects communication with the way station.

What I claim as my invention, and desire to secure by Letters Patent, is-

The combination of the receiving instrument A with a key, D, in the line, the key I and the receiving instrument at a way station, as and for the purpose set forth.

JOSEPH B. STEARNS.

Witnesses:

o. E. cram, WILLIAM A. HAYES, Jr. 

